Electric discharge tube



3811- 1934. R. R. MACHLETT ELECTRIC DISCHARGE TUBE Filed July 1, 1931 AT ORNEYS Patented Jan 1.30, 1934" UNITED STAT-ES I f I ELECTRIC DISCHARGE TUBE I Raymond R. Machlett, Scarsdale, N. Y., as-

signor to Rainbow Light, Inc., Long Island City,

a corporation of New York Application July 1, 1931. Serial No. 548,081

18 Claims.

This invention relates to electric discharge tubes and is concerned more particularly with a discharge tube of novel construction capable of being started and operated at relatively low volt ages comparable with the operating voltages of incandescent lamps and having, if desired, a physical construction such that the new tubes may be mounted in ordinary lamp sockets. The new tubes are of the type which emits light from the positive column and may be employed for a number of purposes, such as for illumination, voltage regulation, rectification, etc.

In my co-pending application Serial No. 507,114, filed January '7, 1931, of which this application is a continuation in part, and in my co-pending application Serial No. 464,077, filed June 26, 1930, I have described electric discharge tubes of the low voltage type which comprise an envelope with a gaseous filling, spaced electrodes within the envelope, and means providing a pair of paths through the envelope between the electrodes. One of these paths has a rising voltage characteristic and the other a falling voltage characteristic and one path includes means for the emission of ions disposed in the space between the electrodes occupied by the positive column. This means may conveniently take the form of a pair of metallic strips, each connected at one end to the electrodes and the strips having their ends spaced apart a short distance at a point between the electrodes.

In this device, the starting path for the discharge includes the strips and at any instant during operation, the end of the strip which is connected to the cathode is covered with a close fitting cathode glow. As current flow continues, the glow spreads along the strip and ultimately the current seeks the second path which is through the gas between the electrodes.

In my co-pending application Serial No. 464,077, I have described in detail the principles on which this type of device is based and in application Serial No. 507,114, I have described the use of a strip connected to one of the electrodes and terminating just short of the other. In my present device, I employ two sets of strips, one connected to each electrode, and each strip extending substantially half the length of the positive column with the free ends of the strips spaced a short distance apart. Also, in the present application, there is disclosed a novel form of electric discharge tube having a physical construction similar to an ordinary incandescent lamp so that the new device may be employed in an ordinary socket.

The tubes of the present invention are for relatively low voltages of the order of 220 volts or less, and one form of the tube which includes a gaseous filling of neon is operable at 110 volts. while another form which includes a gaseous filling of argon-mercury is operable at 200 volts or less and may be readily constructed to operate at a lower voltage of 110. In both cases, the tubes start at substantially lower voltages.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which Fig. 1 is a view in longitudinal section of one form of the invention preferably employed with a neon filling;

Fig. 2 is a sectional view on the line 2-2 of Fig. '3;

Fig. 3 is a view in side of the tube;

Fig. 4 is a longitudinal sectional view of a modified construction, preferably employed with an argon mercury filling, and

Fig. 5 is a plan view of in Fig. 4.

In the drawing, in the device as illustrated in Fig. 1 includes an envelope 10 of glass in any desired form but preferably in the form of a. bulb such as is commonly employed in incandescent lamps. This bulb is provided at one end with a base consisting of a threaded metal cup 8 11 containing a body of insulating material 12 and provided with an insulating plug 13 clos ing an opening in the bottom of the cup. On the end of the plug is a metal disc 14 held in position as by means of a rivet 15. The bulb is provided with an' inwardly directed hollow stem 16, in which is disposed a tube 17 for pumping purposes, the tube being open at 18 to the interior of the bulb and having its tip 19,sealed ofi.

Mounted on top of the stem is a supporting 99 plate 20 for a pair of glass tubes 21 and between the tubes, the stem has a projection 22 in which is mounted a metal support 23 to which the tubes are anchored, for example, by wires 24, each tube being held by its wire to the supporting rod 23. Within each tube is a cylindrical electrode 25 supported by means of a strap 26. This strap may conveniently have a portion secured as by spot welding or the like to the end of a lead 27a or 271) extending through the stem 16 and passing through an opening in the plate 20. The strap may pass up through the interior of the electrode through an opening formed in the wall thereof and extend downwardly on the outside and engage the lower edge of the electrode. At- 110 elevation of a portion certain parts shown tached to the strap at the lower end of each electrode is avessel 28 which contains material used for treating the electrodes. One of the leads 27a passes down through the stem and makes electrical connection as *at 29 with the cup 11, while the other is connected to one terminal of a resistor 30, the other terminal of which is connected to the rivet 15.

Connected electrically to each electrode, as, for example, by being riveted to the strap 26, is a starting strip 31. This strip passes out through the open top of the electrode through the tube 21 and over the edge of the tube to a point adjacent the supporting rod 23. The upper end of the support carries a plurality of leaves of mica 32 and the strip from each electrode is passed between a pair of leaves and then bent around the outer leaf as indicated at 33. With this arrangement, the strips connected to the two electrodes are secured in the same support but electrically insulated from one another by means of the intervening mica leaf.

The tube illustrated in Fig. l is preferably employed with a neon filling and the neon is present at a pressure from 8 to 15 mms. with approximately 10 mms. the preferred pressure. The electrodes employed are preferably of carbon impregnated with an alkali metal as disclosed in my prior Patent No. 1,680,272. The strips 31 are preferably of magnesium with a coating of barium compound, such as barium azide. In the vessels 28, I introduce a material which functions in the preliminary processing of the tube to produce the metallic vapor with which the electrodes are impregnated. I prefer to employ caesium as the impregnating metal and various compounds of caesium such as caesium carbonate, together with a quantity of graphite in the form known commercially as Aquadag has been found to give satisfactory results.

In the operation of the tube illustrated in Fig. 1 on alternating current, the electrodes become anodes and cathodes alternately. During the period when an electrode is functioning as an anode, the strip attached to the other electrode functions as a cathode and becomes covered with a close fitting cathode glow which passes along the strip until the strip is encompassed or nearly encompassed, whereupon the current seeks the gaseous path between the electrodes. This operation is reversed with each half cycle of cur rent.

The tube of the construction illustrated in Fig. 1 may operate with a neon filling at about 110 volts, and with a starting voltage of under 100 volts. The electrodes are of the type known as cold electrodes and the tube will operate at a lower voltage and with higher efficiency and intensity if standard electron-emitting electrodes are employed.

In Fig. 4, there is illustrated a modification of the construction illustrated in Fig. 1 containing a gaseous filling of argon and mercury vapor and to function at about 200 volts with a starting voltage considerably lower and as low as 110 volts. In this tube, the construction is generally the same as that shown in Fig.7 1 except that the electrodes 34 are iron cylinders, such as copper plated Swedish iron and the strips 35 are of iron secured to the electrodes by spot welding or the like. Also, the electrodes may be spot welded to the ends of the leads 27a and 27b. In this tube, the'central supporting rod 36 of slightly modifled construction is provided with forked ends 37 which engagethe-sides of the glass tubes 21 to keepthem spaced a proper distance. Also, the strips 35 which pass up through the tubes 21 are bent over the edges of the tubes as at 38.

In a tube emitting blue or green light and containing argon and mercury vapor, the electrodes and strip must be made of a material which is notafiected by the mercury and for that reason iron electrodes and iron strips are employed in-,

stead of those previously described. The use of iron electrodes and an iron strip increases the voltage at which the blue tube starts and operates but such a blue tube may be made to start and operate at a voltage of about 110 if the electrodes are made of or coated with mercury. Also, the tube may be made to operate at lower voltages and at higher efiiciency and intensity by employing elecron emitting electrodes of standard construction.

In both constructions, it will be noted that the short glass tubes serve to prolong the discharge and cause it to pass from one electrode up through its tube to the free space at the top of the bulb and down through the other tube to the other electrode. The strips lie in the space occupied by the positive column and serve as a source of ions during the starting period. I

In the operation of the tubes of my invention, the application of potential to the electrodes causes the end of the strip which is connected to the cathode to function as a cathode and a close fitting cathode glow is developed at the end of this strip and spreads along it as the current flow increases until ultimately the current seeks the gaseous path between the electrodes and the strip drops out of circuit compleiely or almost completely. I have found that current density is not uniform throughout the length of the cathode strip during the starting operation,

a phenomenon which diifers from that which ocours in the case of an ordinary cathode. Particularly when the tube diameter is small, in the order of 12 mms., the current density tends to become abnormal at the end of the cathode strip where the cathode glow starts at a time when current density is normal elsewhere. By reason of this condition, the strip is likely to sputter unduly. The period during which the sputtering occurs is that in which the glow is spreading along the cathode strip and if a long single strip is employed connected to one electrode only and extending to a point near the other electrode, the use of such a strip would be likely to involve serious sputtering difficulties.

In the new construction described, I employ two strips, one connected to each electrode so that the length of the cathode strip is about half the length that would otherwise be required. Because of this reduction in length, there is less opportunity for the current density on the strip column portion of the tube would, therefore, be

lighted only every other alternation. With the construction disclosed in which there is a strip connected to each electrode and those strips extend substantially half the distance between the electrodes, the effect is that of two tubes function'ng alternately and the two tubes produce the impression of continuous operation. Also, sput- .tering is greatly reduced for the reasons above specified.

What I claim:

1. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrode within the envelope, a pair of tubes aligned with said electrodes and serving to prolong the discharge between the electrodes, said .tubes opening into said envelopeat a place remote from said electrodes, and a pair of electrocon-ductive elements, each connected. electrically to one electrode and extendingalong its tube and out into the envelope.

2. An electric discharge tube which comprises an envelope containing a gaseous filling,

a pair of electrodes within the envelope, a pair of tubes aligned with said electrodes and serving to prolong the discharge between the electrodes, said tubes opening into said envelope at a place remote from said electrodes, and a pair of electro-conductive elements, each connected electrically to one electrode and extending along its tube and out into the envelope, the free ends of said elements being held by a common support but insulated from each other.

3, An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrodes within the envelope, a pair of tubes aligned with said electrodes and serving to prolong the discharge between the electrodes, said tubes opening into said envelope at a place remote from said electrodes, and a pair of fiat metallic strips, each connected electrically to one electrode and extending along its tube and out into the envelope.

4. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrodes within the envelope, a pair of tubes aligned with said electrodes and serving to prolong the discharge between the electrodes, said tubes opening into said envelope at a place remote from said electrodes, and a pair of magnesium strips, each connected electrically to one electrode and extending along its tube and out into the envelope.

5. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrodes within the envelope, means within the envelope for prolonging the discharge between the electrodes, and a pair of electro-conductive elements, each connected electrically to an electrode and extending therefrom along the path of the discharge, the ends of said elements remote from said electrodes lying close together.

6. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair ofelectrodes within the envelope, means within the envelope for prolonging the discharge between the electrodes, and a pair of metallic elements, each connected electrically to one electrode and extending toward the other electrode along the path of the discharge, said elements having their ends remote from said electrodes lying close to- I gether.

prolong the discharge between the electrodes and confine it for a portion of its length, and a pair of electro-conductive elements, each connected electrically to an electrode and extending through the tube aligned with said electrode and out into the mainbody of gas in the envelope, said elements having free ends adjacent each other in said main body of gas.

8. An electric discharge tube which comprises an envelope containing a gaseous filling-, a pair of electrodes within the envelope, a pair of tubes, each aligned with an electrode and arranged to prolong the discharge between the electrodes and confine it for a portion of its length, and a pair of electro-conductive elements, each connected electrically to an electrode and extending through the tube aligned with said electrode and out into the main body of gas in the envelope, the free ends of said elements being mounted in a common support in the main body of gas and insulated from each other.

9. An electric discharge tube which comprises an envelope containing of electrodes within the envelope, said electrodes being'porous, means within the envelope for prolonging the discharge between the electrodes, a pair of electro-conductive elements, each connected electrically to one electrode and extending toward the other, said elements having adjacent ends in the main body of gas within the envelope, and means within the envelope capable of evolving a fluid during processing of the tube, said fluid being absorbable at least in part by said porous electrodes.

10. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrodes within the envelope, said electrodes being porous, means within the envelope for prolonging the discharge between the electrodes, a pair of electro-conductive elements, each connected electrically to one electrode and extending toward the other, said elements having adjacent ends in the main body ofv gas within the envelope, and a metallic vessel within the envelope containing a substance evolving a fluid during processing of the tube, said fluid being at least in part absorbed by said electrodes.

11. An electric discharge tube which comprises an envelope containing neon, a pair of carbon electrodes within the envelope, means within the envelope for prolonging the discharge between the electrodes and confining the discharge for at least a part of its length, and a pair of -magnesium elements, each connected electrically to one electrode and extending toward the other, the free ends of said elements lying substantially adjacent and at a. place where said discharge is unconfined by said means.

12. An electric discharge tube which comprises an envelope containing a gaseous filling of argon-mercury, a pair of iron electrodes within the envelope, partition means within the envelope for prolonging the discharge between the electrodes, a pair of electro-conductive strips, each connected electrically to one electrode and extending toward the other, said strips having ends remote from said electrodes lying in that part of the envelope occupied by the discharge unconfined.

13. An electric discharge tube which comprises an envelope containing a gaseous filling, a pair of electrodes within the envelope, a glass tube aligned with each electrode, said tubes having open ends remote from said electrodes and prolonging the discharge between the electrodes and confining it for a portion of its length, and a pair of electro-conductive elements, each connected electrically to one electrode and extending a gaseous filling, a pair through the tube aligned therewith and out the end of said tube;

14. An electric discharge tube which comprises an envelope containing a gaseous filling, a stem within the envelope, a pair of electrodes mounted side by side at the end of the stem, partition means on the stem extending toward the remote wall of the envelope and adapted to prolong the discharge between the electrodes, and a pair of electro-conductive elements, each connected electrically to one electrode and extending along the path of the discharge, said elements having their ends remote from said electrodes lying close together.

15. An electric discharge tube which comprises an envelope containing a gaseous filling, a stem within the envelope, a pair of electrodes mounted side by side at the end of the stem, a pair of tubes mounted on the stem, each tube having a closed end near the stem and receiving an elec trode near its closed end, the other end of each tube being open, and a pair of electro-conductive elements each connected electrically to an electrode and extending through its tube and out the open end thereof.

16. An electric discharge tube which comprises an envelope containing a gaseous filling, a stem within the envelope, a pair of electrodes mounted side by side at'the end of the stem, a pair of tubes mounted on the stem, each tube having a closed end near the stem and receiving an electrode near its closed end, the other end of each tube being open, and a pair of electro-conductive elements, each connected electrically'to an electrode and extending through its tube and out the open end thereof, the ends of saidelements outside the tubes being secured to a common support and insulated from each other.

17. An electric discharge tube which comprises an envelope containing a gaseous filling, a stem within the envelope, a pair of electrodes mounted side by side at the end of the stem, partition means on the stem prolonging the discharge between the electrodes, a vessel adjacent each elec trode containing a substance which evolves a vapor during heat processing ofthe discharge vapor during heat processing of the discharge tube, and a metallic element connected electrically to each electrode and extending along the path of the discharge between the electrodes, said elements having their ends remote from the electrodes connected mechanically but not electrically.

RAYMOND R. MACHLETT. 

